Wind generators of various types for generating electricity using wind are known well. The invention relates to a horizontal axle blade unit having spiral blades. Prior arts of each spiral blade mentioned in the invention are described in detail in an international application publication WO 2011/142653 A1 (referred as ‘previously-filed invention’ below). The technological contents related to each blade described in the international application publication is incorporated by reference as a prior art to the invention by citing the international application publication.
In general, the wind generator includes a blade unit comprising a rotational axle and a plurality of blades engaging the rotational axle and disposed around the rotational axle for obtaining rotational torque from wind.
The blade unit having spiral blades is difficult to manufacture integrally by injection molding or casting due to a designing structure of preferably three blades.
Therefore, spiral blades are manufactured individually separately from the rotational axle, and then must be fixed to an outer circumferential surface of the rotational axle strongly with even intervals. In order to fix the spiral blades strongly, it was tried that a frame is installed on the rotational axle's outer circumferential surface having a hexagonal cross-section using bolts and a root portion of each blade is to be fixed to the frame using bolt and nut, but there were problems that strength of the rotational axle was weakened due to multiple bolt hole, weight of the spiral blade unit increases a lot due to the usage of many bolts and nuts, engaging bolt and nut are loosened if used for an extended time period, and it takes long hours to manufacture and assembly the rotational axle and frames.